(1) Field of the Invention
This invention generally relates to automotive rear suspension systems, and particularly relates to multi-link suspensions with five I-links.
(2) Description of the Related Art
There have been known conventional multi-link suspensions with five I-links, each I-link including a resilient bush at least at an end thereof located toward the vehicle body (see, for example, Japanese Unexamined Patent Publication No. 2-38106). In such a multi-link suspension with five I-links, I-links can be arranged to optimally constrain movement of the rear wheel in accordance with five-way freedom of movement of the rear wheel except for up and down strokes. Therefore, this suspension is of the type having great performance potential.
Problems that the Invention is to Solve
However, multi-link suspensions generally have a problem about rigidity, and this problem is particularly noticeable in the above-described structure in which links are mounted to a suspension member through resilient bushes. Specifically, when the wheel receives a side force during cornering, the resilient bush for each link deflects to give the driver a sense of reduced rigidity and produce a delay of suspension response corresponding to the deflection.
Furthermore, the wheel alignment depending upon how the links are geometrically arranged changes by the amount of deflection of the resilient bushes. The high design flexibility of the multi-link suspension makes it very difficult to design and manage the resilient bushes to deflect in respective optimal directions even when they input any load. Therefore, it is difficult that the multi-link suspension exhibits suspension performance as expected.
In view of these points, multi-link suspensions are generally employed for classy sedans and the like which place emphasis on ride quality rather than handling stability and require high straight running stability during high-speed running rather than cornering performance. As a matter of fact, they are not employed for sports cars and the like which place severer requirements on handing stability and cornering performance in limit maneuvering conditions than on ride quality.
If the multi-link suspension did not employ any resilient bushes and all the links were connected to the vehicle body through ball joints, there would not be caused any problem due to deflection of the bushes. This not only provides enhanced rigidity and response but also enables the alignment accuracy to be maintained in an intended state. It therefore goes without saying that the suspension can achieve an excellent handling stability in combination with its fundamentally high potential. In this structure, however, vibration and noise absorption to be contributed by resilient bushes will not be expected at all. Thus, road noise is increased, and noises caused by link resonance and other noises are all transmitted to the vehicle body, which makes it impossible to put the suspension into practical use for a passenger car. Also in this respect, the multi-link suspensions with five I-links are difficult to employ for commercial type cars, even if sports cars, which are required to perform vibration and noise absorption.
In view of the foregoing problems, it is an object of the present invention to provide a multi-link rear suspension system with five I-links, each I-link including a resilient bush at least at an end thereof located toward a vehicle body, based on a completely new knowledge that the suspension can exhibit sufficient anti-vibration performance for a commercial type car while ensuring a high handling stability applicable for a vehicle that requires high performance as a sports car.